Question: Solve for $z$ : $z - 30 = -19$
Add $30$ to both sides: $ \begin{eqnarray} \\ z - 30 &=& -19 \\ \\ {+30} && {+30} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{-30 + z} &\hphantom{=}& \hphantom{-19} \\ z &=& -19 {+ 30} \\ \end{eqnarray} $ Simplify. $ z = 11$